It is known that in intensive-care wards, where the patient is ventilated artificially with a respirator, heated humidifiers are usually used which are placed along the inspiratory line and are capable of providing a level of humidity and heat that the upper air passages of the patient, having been bypassed, cannot ensure, in order to maintain ordinary mucociliary functions.
Currently commercially available humidifiers heat the gases supplied by the ventilator and load them with humidity; in order to ensure the sterility of the inspiration gases, the water that is ventilated for humidification is necessarily sterile.
However, despite the use of sterile water, sterility conditions are not maintained, since in conventional active humidifiers the gas becomes loaded with humidity by flowing over the water surface. With this arrangement, the aerobic bacterial loads present in the incoming gases necessarily contaminate the heating bath.
The particular environmental condition, with the presence of humidity and heat, is the ideal medium for the proliferation of bacterial loads.
Furthermore, in addition to this type of contamination, the bath is also contaminated by means of the condensation that forms along the line that connects the humidifier to the patient; this condensation acts as a vehicle for the bacterial loads that are present in the air expired by the patient.
Accordingly, after a period of approximately two or three hours of operation, very high concentration of bacterial loads forms inside the humidification chamber; these loads constitute a severe risk of cross-infections for the patient.
With the conventional solutions, therefore, humidifiers are used which require the use of sterile water for their operation but do not allow to maintain sterility conditions.
U.S. Pat. No. 4,943,704 discloses a humidifier apparatus for admixture of heated water vapor into a gaseous stream, including a water heating platen, and a disposable vapor transfer chamber formed by a hydrophobic filter membrane supporting structure and a cover. The supporting structure is arranged over the water heating platen such that the filter is arranged above and extends parallel to the platen whereby heated water vapor rises through the filter and into the cover, which is provided with gas intake and discharge ports, to mix the heated water vapor into the gaseous stream.